A map of the Moon 10-times older than anything known before has been found carved into stone at one of Ireland's most ancient and mysterious Neolithic sites.

It has been identified by Dr Philip Stooke, of the University of Western Ontario, Canada. He spends most of his time preparing maps of asteroids based on spacecraft observations, but he has also prepared detailed maps of the Moon.

What puzzled him greatly was that there was no recorded map of the Moon older than about 500 years. "I simply could not believe this," he told BBC News Online. "I felt there just had to be an older map somewhere."

Prehistoric tombs

So he began looking in old manuscripts and history books as well as in the records of excavations of the Neolithic sites on the British Isles.

Then he found one. It took the eye of an expert to see it for what it was. It was carved into a rock in one of Ireland's most remarkable prehistoric tombs at Knowth, County Meath.

"I was amazed when I saw it. Place the markings over a picture of the full Moon and you will see that they line up. It is without doubt a map of the Moon, the most ancient one ever found," said Dr Stooke.

"It's all there in the carving. You can see the overall pattern of the lunar features, from features such as Mare Humorun through to Mare Crisium."

Before this discovery, the oldest known map of the Moon was by Leonardo da Vinci, drawn about 1505. The Knowth map is 10-times older.

Knowth is already a major focus of research into understanding prehistoric man. Now, it will become one of the most important scientific sites in the world.

"The people who carved this Moon map were the first scientists," said Dr Stooke. "They knew a great deal about the motion of the Moon. They were not primitive at all."

The passage tomb at Knowth is estimated to be about 5,000 years old. It was obviously built by men who had a sophisticated understanding of the motions of the Sun, Moon and stars.

It is known that many stone circles and ancient tombs are aligned with the Sun but less attention has been paid to possible lunar alignments. This is despite the fact that at certain times the Moon can rise or set at any location on the horizon that the Sun can.

Series of arcs

Investigations at Knowth almost 20 years ago showed that at certain times moonlight could shine down the eastern passage of the tomb.

Remarkably, the moonlight would also fall on the Neolithic lunar map.

During excavations, the stone in question was named Orthostat 47. Its right-hand section contains a series of arcs.

The circular limb of the moon is not included in the carving. Dr Stooke believes that it may have been drawn on the rock with chalk or with coloured paint.